We are proposing a comprehensive study of the central thermoregulatory mechanism in the Yucatan miniature pig. This investigation will involve measuring the temperature threshold and sensitivity for thermoregulatory responses. The responses to be measured are rate of heat production, rate of respiratory evaporative heat loss, rate of blood flow to the tongue and skin and rate of flow of saliva from the parotid duct. The central thermoregulatory mechanism will be probed by inducing physiological states thought to alter the thermoregulatory "set point" (eg. fever, exercise) and determining their effect on the threshold and sensitivity of the thermoregulatory responses. Because the magnitude of a thermoregulatory response is dependent, in part, on the input from temperature sensors located throughout the body we will manipulate the extrahypothalamic core temperature (Tehc), hypothalamic temperature (Thy), and skin temperature (Tsk) independently of each other. Although knowing the input from the Tehc is crucial to interpreting the significance of threshold and gain shifts, the technique for altering Tehc has been developed and used only recently. In our experiments Tehc will be manipulated with an extra-corporial heat exchanger. They will be manipulated with thermodes and Tsk will be altered by changing ambient temperature (Ta). The other technique important to this investigation is the use of physiological states thought to alter the thermoregulatory "set point". The effect of these states on the threshold and sensitivity of thermoregulatory responses is one of the few tools we have for studying the nature of the central thermoregulatory mechanism and will be used extensively in this investigation. The results of this investigation will contribute to our understanding of the mammalian central thermoregulatory mechanism. Because we have chosen the miniature pig as the subject of these experiments, the information will also be of importance to cardiovascular, exercise and respiratory physiology for which the miniature pig is often used as a model for human physiology.